1. Field of the Invention
The invention relates to the field of ultrasonic (including megasonic and gigasonic) treatment of substrate surfaces.
2. Description of Related Art
Removal of particulate contaminants from a semiconductor substrate can be accomplished by ultrasonic cleaning. When the frequency of ultrasound is close to or above 1,000 kHz (1 MHz) it is often referred to as “megasonic”. When the frequency of ultrasound is close to or above 1,000 MHz (1 GHz) it can be referred to as “gigasonic”. Conventional techniques for ultrasonic cleaning of semiconductor wafers rely upon cavitation effects, in which the ultrasonic energy induces the formation of small bubbles, the collapse of which releases high quantities of energy into the surrounding fluid, and promotes cleaning of substrates.
However, excessive cavitation energy near a substrate having delicate surfaces or components can also cause substrate damage.